I know its lame advice but how about you wear what you feel comfortable in that still looks professional? You say you sell to technical people so if you know your product and the technical details of its application and can discussion how it might improve their respective environment/configuration are they likely to even notice your attire, even more so because they are technical people?
All im saying is how about you get a suit which looks good on you and worry about the formality of it later? For example a great suit with a nice shirt, unbuttoned top button and no tie looks a lot less formal regardless of the quality or nature of the suit. Slickness (in a manner that may erode credibility and remind people of gordon gecko) is always going to come from how you wear it and what you wear it with - rather than the suit itself (for the most part).
Maybe a suit isn't for you yet, a sportscoat with the right trousers and shirt can still look professional without being too formal.
Hmmm, I'll still have a chat with the guys at the SuitShop and see what they say. Of course they'll want to sell me a suit. I have not worn a suit since my 20s, when I worked as an Accountant. Nowadays in I.T. and glad to work around more relaxed environments. But still in my 40s and think I need to get back into the suit thing without the formality and have it feel as normal as jeans and a white t-shirt on Saturdays.
Thanks for the lengthy response. I appreciate it.